Solve the following trig equation for 0°≤θ

Question

Solve the following trig equation for 0°≤θ<360°
-9cosθ+5=6cosθ+1

dls · Answer

Rearrange the equation to get : 
15 cos theta = 4
and solve for theta

anonymous · Answer

=>16 cos theta=4
=> cos theta= 1/4
=>theta= cos^-1(1/4)
=>theta=75.52

dls · Answer

9+6=15

dls · Answer

my dear human calculator :)

dumbcow · Answer

you will need to use your calculator to do inverse cos
$$\theta = \cos^{-1} \frac{4}{15}$$
Note you will have 2 solutions in 1st and 4th quadrants because cos is positive

dumbcow · Answer

|dw:1405883093640:dw|

anonymous · Answer

like i don't understand the whole proccess :$

dumbcow · Answer

which part?

anonymous · Answer

how is there 16 and 15 in the first 2 answers?

dumbcow · Answer

from using algebra to combine terms and isolate the cos

ignore the 16, it was a typo or simple mistake in adding

anonymous · Answer

huh okay, then how about this equation: 

Solve the following trig equation for 0°≤θ<360°
-4cos2θ=-3

anonymous · Answer

i don't really understand the general idea so maybe another example may be helpful @dumbcow :4